The present invention concerns an articulating device with automatic adaptation to the registered condyle distance.
It is already well known that an articulator is a subsidy for odontotechnicians, as it simulates the cranio-facial skeleton limited to the upper jaw, to the mandible and to the temple-mandible articulations.
The bone structure of the articulations consists of two fix elements, one for each side, inserted at the basis of the cranium, shown as glenoid cavities, and of two movable elements, the condyles, united one to the other by means of the mandible body.
The condyles get placed at the center of the relative glenoid cavities when the mouth is in an occlusion position, i.e. in the position of maximum intercuspidation.
When the mandible moves, the condyles inside the glenoid cavities move in synchrony; these movements are complex and tridimensional.
In the articulator, the upper branch shows the jaw, and the lower branch looks like a mandible, while the articulations have been transformed into mechanisms placed in part on the upper branch, in part on the lower branch.
The articulators may be divided in two kinds: those that have the condylar part in the lower branch and the glenoid part in the upper branch and are called ARCON, i.e. articulating condyles, and those non-ARCON, that have the condyles in the upper branch and in the lower branch are provided with a system that simulates the glenoid cavity.
The articulator may be personalized by adapting the mechanism that simulates the articulations to determined movements that the condyles perform in the glenoid cavity.
Those movements, that are called condylar distances and shown like the edge or limit within which the functional movements of the mandible are performed, may be realized by means of extra-oral or intra-oral registrations.
The extra-oral registrations make use of a pantograph system that is placed onto the face and is blocked onto the mandible and the jaw, and by means of printers, lay-outs are obtained that are transferred onto adaptable articulators that are compatible with this kind of registration.
For what concerns the intra-oral registrations, waxes are used that are indented by the mandible when the latter gets from a central position to a lateral-projecting one. Wax indentations will be performed first on one side and then on the other side. The distance that must be covered by the condyle from the central to the lateral-projecting position is transferred onto adaptable articulators in the mechanism simulating the articulations.
After having obtained the chalk casting (models) of the two arches, the use process may be described as follows:
1. the upper model is plastered, in a correct position, onto the upper branch of the articulator by means of an appropriate instrument (transfer facial arch); PA1 2. once the articulator has been turned upside-down, the upper model will be incuspidated to the lower one that will be plastered to the lower branch; PA1 3. with thermoplastic material a base will be prepared, on the upper model, that covers part of the palate and of the occlusion surface limited to the molar and premolar teeth; this base will be realized in double copy; PA1 4. a plurality of wax thicknesses are made to adhere on the two sides of the occlusion surface of the bases; the softened wax registers the lateral-projecting indenting; PA1 5. once the base has been placed onto the palate, in the mouth the lateral-projecting positions of the mandible will be registered, e.g., first from right to left and then from left to right. PA1 A) the first position is when the mandible is centrated in occlusion; the condyles are placed at the center of the glenoid cavity; PA1 B) the second position is when the mandible is laterally-projecting; from the side of the lateral projection, the condyle is placed forewardly on the bottom and inside moves of about 1.00 cm, while on the other side, it is placed upward and backward of 0.1 to 0.2 cm. PA1 1. the base with the registration wax will be moved from the mouth to the upper model; PA1 2. once the mechanisms showing the articulations have been loosened, the chalk model of the lower arch will be indented to the wax registered in the mouth.
Now the intra-oral registration considers only two positions of the condyles inside the glenoid cavity:
From the ideal union between the two condylar positions--the central one and the lateral-projecting one--the condylar distance is obtained.
As the distance covered by the condyle in its lateral-projecting movement takes place in three dimensions, the mechanical system that simulates the glenoid cavity rotates simultaneously around the transversal axis realizing an inclination from top to bottom and from back to front, together with an inclination that rotates around the vertical axis with an inclination to the inside, from back to front.
These distances may be quantified in grades; on the sagittal plane the inclination of the condylar distance may be registered toward the bottom, and on the horizontal plane the inward deviation of the condyle will be registered.
The transferring of the extra-oral and intra-oral registrations is really very difficult when passing from the mouth to the articulator, and therfore, compromises must be accepted when the mechanical parts are adapted to the condylar distances.
Even if the fundamental structures and the difficulties are the same, criticisms are mainly turned to the adaptable articulators with intra-oral registration with the purposes of showing the needs being the base of the present invention.
All articulators are composed of an upper part and a lower part; the latter shows the mandible.
That part of the articulator showing the mandible consists in turn of a horizontal branch and two vertical branches, like the vertical branches of the mandible.
Their feature is the one of being fixely jointed, like in nature, to the horizontal branch.
This immobility is partially corrected in some articulators in which the vertical branches may perform, along a well delimited transversal axis, only a translatory movement toward the inside or the outside according to the intercondylar distance that is calculated in average about 11.00 cm.
As the mandible is more or less great, a greater or smaller intercondylar distance may be transferred in some articulators by means of facial measurings or by means of the lateral movement.
Furthermore, such measurings appear to be non relevant for the purpose of obtaining a better adaptation of the articulator to the condylar distance. In fact, the mandible moves onto immediate centers that will never intersect with the condyles.
The most relevant need is the one of obtaining an exact relevation of the lateral-projecting position of the mandible from the mouth to the articulator.
When the wax that has registered the lateral-projecting position of the mandible, is transferred from the mouth to the articulator, the immobility of the vertical branches does not allow a monolateral registration, but always includes the two mechanisms that disturb and influence one another.
Practically, once the chalk models have been placed in the two arches of the articulator and the lateral-projection has been registered in the mouth on one side,
This operation appears to be very difficult because the registration of the condylar distance of the side where the condyle moves frontwardly, downwardly and inwardly is disturbed by the contemporary movement toward the top of the counter-lateral condyle.
As the two condylar distances may not be registered at the same time, the indentation of the registered wax on the side of the model fixed in the articulator, implies forcings that constrain and deform the wax forcing the operator to accept compromises.
A further serious inconvenience consists in that the mechanical elements of the articulations do not get automatically adapted to the registered condylar distance, but must be guided and corrected by the operator, which means that where oscillations are noted, the registration of the condylar distance is completely distorted.